Interference aware reciprocal channel sounding reference signal

ABSTRACT

Systems, devices, and methods associated with interference aware sounding reference signals are provided. A method for wireless communication includes receiving, at a wireless communication device in communication with a first base station, an interfering signal from a second base station (or other base stations); determining, at the wireless communication device, a spatial direction of the interfering signal; and transmitting, with the wireless communication device, a signal to the first base station based on the spatial direction of the interfering signal. Another method of wireless communication includes receiving, at a first base station, a signal from a wireless communication device, the signal based on a spatial direction of an interfering signal received by the wireless communication device from a second base station (or other base stations); transmitting, with the first base station, a downlink communication to the wireless communication device, the downlink communication beamformed in the spatial direction based on the signal received from the wireless communication device.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/866,768, filed Sep. 25, 2015, which claimspriority to and the benefit of the U.S. Provisional Patent ApplicationNo. 62/133,366, filed Mar. 14, 2015, each of which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

This application relates to wireless communication systems, and moreparticularly to improving communications between user equipment and abase station by accounting for the spatial direction of interferencereceived by the user equipment.

BACKGROUND

A wireless communication network may include a number of base stationsthat can support communication for a number of user equipments (UEs). Inrecent years, the carrier frequencies at which base stations and UEscommunicate have continued to increase and include larger bandwidths. Totake advantage of these higher frequencies, more antennas in the samephysical space have been used. For these higher frequency bands to beuseful and approximate the same coverage radius as prior technologies(such as 2G, 3G, or 4G), however, more beam forming gain (and moreaccurate) is becoming necessary.

Further, conventional systems employ various types of reference signals,with varying fixed structures, to provide sufficient measurements andestimations for adaptive multi-antenna operation in uplink and/ordownlink directions. For example, a channel state information referencesignal (CSI-RS) may be used on a downlink from the base station to aidthe base station in beam form determination, an uplink demodulationreference signal (DM-RS) specific to each UE may be used to estimatechannel information for the uplink specifically, and each UE may use asounding reference signal (SRS) on the uplink to aid in scheduling(e.g., determining which frequency bands are good or bad for data).There is no single signal that is able to achieve all of abovefunctionality for UEs.

Reciprocity describes the ability for a station to use information (suchas a multipath delay profile) from one channel (e.g., the uplink) inmaking determinations regarding another channel (e.g., the downlink).Reciprocity has not been available for cellular networks because currentapproaches require reference signals specific for particular antennas,such as CSI-RS in the long term evolution (LTE) context. Further, CSI-RSand other types of signals do not scale well, which is becoming anever-increasing issue as the demand for mobile broadband continues toincrease.

In addition to intended communication received from the base station,user equipment can also receive interfering signals. These interferingsignals can arise from a variety of sources. For example, theinterference can be the result of established communication channelbetween another device and another base station. Communication betweenuser equipment and base stations is hampered when intended downlinkcommunication is received along with interference.

SUMMARY

In an aspect of the disclosure, a method for wireless communication isprovided that includes receiving, at a wireless communication device incommunication with a first base station, an interfering signal from asecond base station (or other base stations); determining, at thewireless communication device, a spatial direction of the interferingsignal; and transmitting, with the wireless communication device, asignal to the first base station based on the spatial direction of theinterfering signal.

In another aspect of the disclosure, transmitting the signal to thefirst base station includes: transmitting a beamformed soundingreference signal (SRS) to the first base station. In another aspect, thebeamformed SRS has a spatial direction that limits interference from theinterfering signal. In another aspect, the beamformed SRS is establishedbased on a beam codebook. In another aspect, the beamformed SRS isestablished based on a calculation associated with interference from theinterfering signal. In another aspect, the method further includesreceiving, at the first wireless communication device, a downlinkcommunication from the base station, wherein downlink communicationlayer are beamformed in the spatial direction(s) based on the signaltransmitted to the first base station. In another aspect, thetransmitting the signal to the first base station includes:transmitting, with the wireless communication device, multiple signalsto the first base station based on the spatial direction of theinterfering signal. In another aspect, the multiple signals aretransmitted simultaneously. In another aspect, the multiple signals eachhave a different phase. In another aspect, the multiple signals aretransmitted sequentially over time. In another aspect, the multiplesignals each have a different phase. In another aspect, the transmittingthe multiple signals includes: transmitting at least one soundingreference signal (SRS) via a first antenna of the mobile communicationdevice at a first time; and transmitting at least one SRS via a secondantenna of the mobile communication device at a second time.

In another aspect of the disclosure, a method for wireless communicationis provided that includes receiving, at a first base station, a signalfrom a wireless communication device, the signal based on a spatialdirection of an interfering signal received by the wirelesscommunication device from a second base station (or other basestations); transmitting, with the first base station, a downlinkcommunication to the wireless communication device, wherein downlinkcommunication layers are beamformed in the spatial direction(s) based onthe signal received from the wireless communication device.

In another aspect of the disclosure, the receiving a signal from thewireless communication device includes: receiving a beamformed soundingreference signal (SRS). In another aspect, the beamformed SRS has aspatial direction that limits interference at the wireless communicationdevice from the interfering signal. In another aspect, the methodfurther includes establishing, at the first base station, acommunication channel between the first base station and wirelesscommunication device based on the beamformed SRS. In another aspect, thedownlink communication is transmitted using at least one antenna of thefirst base station operable to transmit along the spatial directionbased on the signal received from the wireless communication device, thefirst base station having a plurality of antennas operable to transmitalong different spatial directions. In another aspect, the transmittinga downlink communication includes: transmitting the downlinkcommunication along a path selected from among a plurality of pathsbased on the signal received from the wireless communication device. Inanother aspect, the downlink communication is established based on abeam codebook. In another aspect, the downlink communication isestablished based on a reciprocal beam calculation.

In another aspect of the disclosure, a wireless communication device incommunication with a first base station is provided that includes atransceiver operable to receive an interfering signal from a second basestation (or other base stations); and a computing device incommunication with the transceiver, the computing device operable todetermine a spatial direction of the interfering signal; wherein thetransceiver is further operable to transmit a signal to the first basestation based on the spatial direction of the interfering signal.

In another aspect of the disclosure, the transceiver is operable totransmit the signal to the first base station by transmitting abeamformed sounding reference signal (SRS) to the first base station. Inanother aspect, the beamformed SRS has a spatial direction that limitsinterference from the interfering signal. In another aspect, thecomputing device is further operable to establish the beamformed SRSbased on a beam codebook. In another aspect, the computing device isfurther operable to establish the beamformed SRS based on a calculationassociated with interference from the interfering signal. In anotheraspect, the transceiver is further operable to: receive a downlinkcommunication from the base station, wherein downlink communicationlayers are beamformed in the spatial direction(s) based on the signaltransmitted to the first base station. In another aspect, thetransceiver is operable to transmit the signal to the first base stationby: transmitting multiple signals to the first base station based on thespatial direction of the interfering signal. In another aspect, themultiple signals are transmitted simultaneously. In another aspect, themultiple signals each have a different phase. In another aspect, themultiple signals are transmitted sequentially over time. In anotheraspect, the multiple signals each have a different phase. In anotheraspect, the transceiver is operable to transmit the multiple signals by:transmitting at least one sounding reference signal (SRS) via a firstantenna in communication with the transceiver at a first time; andtransmitting at least one SRS via a second antenna in communication withthe transceiver at a second time.

In another aspect of the disclosure, a base station is provided thatincludes a transceiver operable to: receive a signal from a wirelesscommunication device, the signal based on a spatial direction of aninterfering signal received by the wireless communication device from asecond base station (or other base stations); and transmit a downlinkcommunication to the wireless communication device, wherein downlinkcommunication layers are beamformed in the spatial direction(s) based onthe signal received from the wireless communication device.

In another aspect of the disclosure, a transceiver operable to receive asignal from the wireless communication device by: receiving a beamformedsounding reference signal (SRS). In another aspect, the beamformed SRShas a spatial direction that limits interference at the wirelesscommunication device from the interfering signal. In another aspect, thebase station further comprises: a computing device in communication withthe transceiver, the computing device operable to establish acommunication channel with the wireless communication device based onthe beamformed SRS. In another aspect, the base station furthercomprises a plurality of antennas in communication with the transceiverand operable to transmit along different spatial directions, wherein thedownlink communication is transmitted using at least one antennaoperable to transmit along the spatial direction based on the signalreceived from the wireless communication device. In another aspect, thetransceiver is operable to transmit a downlink communication by:transmitting the downlink communication along a path selected from amonga plurality of paths based on the signal received from the wirelesscommunication device. In another aspect, the base station furthercomprises a computing device operable to establish the downlinkcommunication based on a beam codebook. In another aspect, the basestation further comprises a computing device operable to establish thedownlink communication based on a reciprocal beam calculation.

In another aspect of the disclosure, a wireless communication device incommunication with a first base station is provided that includes meansfor receiving an interfering signal from a second base station (or otherbase stations); means for determining a spatial direction of theinterfering signal; and means for transmitting a signal to the firstbase station based on the spatial direction of the interfering signal.

In another aspect of the disclosure, the means for transmitting a signalto the first base station includes: means for transmitting a beamformedsounding reference signal (SRS) to the first base station. In anotheraspect, the beamformed SRS has a spatial direction that limitsinterference from the interfering signal. In another aspect, the meansfor transmitting a beamformed sounding reference signal (SRS) includes:means for establishing the beamformed SRS based on a beam codebook. Inanother aspect, the means for transmitting a beamformed soundingreference signal (SRS) includes: means for establishing the beamformedSRS based on a calculation associated with interference from theinterfering signal. In another aspect, the wireless communication devicefurther includes means for receiving a downlink communication from thebase station, wherein downlink communication layers are beamformed inthe spatial direction(s) based on the signal transmitted to the firstbase station. In another aspect, the means for transmitting the signalto the first base station includes means for transmitting multiplesignals to the first base station based on the spatial direction of theinterfering signal. In another aspect, the means for transmittingmultiple signals includes means for transmitting the multiple signalssimultaneously. In another aspect, the multiple signals each have adifferent phase. In another aspect, the means for transmitting multiplesignals includes means for transmitting the multiple signalssequentially over time. In another aspect, the multiple signals eachhave a different phase. In another aspect, the means for transmittingmultiple signals includes means for transmitting at least one soundingreference signal (SRS) at a first time; and means for transmitting atleast one SRS at a second time.

In another aspect of the disclosure, a base station is provided thatincludes means for receiving a signal from a wireless communicationdevice, the signal based on a spatial direction of an interfering signalreceived by the wireless communication device from a second base station(or other base stations); and means for transmitting a downlinkcommunication to the wireless communication device, wherein downlinkcommunication layers are beamformed in the spatial direction(s) based onthe signal received from the wireless communication device.

In another aspect of the disclosure, the means for receiving a signalfrom the wireless communication device includes means for receiving abeamformed sounding reference signal (SRS). In another aspect, thebeamformed SRS has a spatial direction that limits interference at thewireless communication device from the interfering signal. In anotheraspect, the base station further includes means for establishing acommunication channel with the wireless communication device based onthe beamformed SRS. In another aspect, the base station further includesmeans for transmitting along different spatial directions, wherein thedownlink communication is transmitted along the spatial direction basedon the signal received from the wireless communication device. Inanother aspect, the means for transmitting a downlink communicationincludes: means for transmitting the downlink communication along a pathselected from among a plurality of paths based on the signal receivedfrom the wireless communication device. In another aspect, the means fortransmitting a downlink communication includes: means for establishingthe downlink communication based on a beam codebook. In another aspect,the means for transmitting a downlink communication includes means forestablishing the downlink communication based on a reciprocal beamcalculation.

Additional aspects, features, and advantages of the present disclosurewill become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication network, in accordance withvarious aspects of the present disclosure.

FIG. 2 illustrates a wireless communication network which uses soundingreference signals to enable beamforming at a base station, in accordancewith various aspects of the present disclosure.

FIG. 3 illustrates an exemplary subframe structure, in accordance withvarious aspects of the present disclosure.

FIG. 4 illustrates a portion of a wireless communication network inwhich an interfering signal is received at user equipment, in accordancewith various aspects of the present disclosure.

FIG. 5 is a flow diagram of a wireless communication method, inaccordance with various aspects of the present disclosure.

FIG. 6 is a flow diagram of a wireless communication method, inaccordance with various aspects of the present disclosure.

FIG. 7 illustrates a portion of a wireless communication network inwhich an interfering signal is received at user equipment, in accordancewith various aspects of the present disclosure.

FIG. 8 illustrates a portion of a wireless communication network inwhich a beamformed sounding reference signal is transmitted from userequipment to a base station, in accordance with various aspects of thepresent disclosure.

FIG. 9 illustrates a portion of a wireless communication network in anomnidirectional beamformed sounding reference signal is transmitted fromuser equipment to a base station, in accordance with various aspects ofthe present disclosure.

FIG. 10 illustrates a portion of a wireless communication network inwhich a downlink communication is transmitted by a base station to userequipment based on a beamformed sounding reference signal, in accordancewith various aspects of the present disclosure.

FIG. 11 illustrates a portion of a wireless communication network inwhich a path is selected among a plurality of paths, in accordance withvarious aspects of the present disclosure.

FIG. 12 illustrates a portion of a wireless communication network inwhich multiple sounding reference signals are transmitted by userequipment, in accordance with various aspects of the present disclosure.

FIG. 13 illustrates a portion of a wireless communication network inwhich multiple sounding reference signals are transmitted by userequipment, in accordance with various aspects of the present disclosure.

FIG. 14 is a block diagram of an exemplary wireless communicationdevice, such as a user equipment, according to embodiments of thepresent disclosure.

FIG. 15 is a block diagram of an exemplary wireless communicationdevice, such as a base station, according to embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). CDMA2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies, such as a next generation (e.g., 5^(th)Generation (5G)) network.

The present disclosure describes communication between user equipment(UE) and a base station that accounts for the spatial direction of aninterfering signal received by the UE. The UE can experienceinterference that results from downlink signals transmitted by anotherbase station to another UE. The UE determines the direction of theinterfering signal and transmits a signal to the base station based onthe direction of the interfering signal. For example, the signal can bea beamformed sounding reference signal (BF-SRS) that has a spatialdirection that limits interference from the interfering signal. The basestation receives the signal from the UE and transmits downlinkcommunication that is beamformed in the spatial direction based on thesignal received from the UE. The base station is thus able to transmit afocused beam that accounts from the spatial direction of interferencereceived by the UE. The UE receives downlink communications along aspatial direction that limits interference.

FIG. 1 illustrates a wireless communication network 100 in accordancewith various aspects of the present disclosure. The wirelesscommunication network 100 may include a number of UEs 102, as well as anumber of base stations 104. The base stations 104 may include anevolved Node B (eNodeB). A base station may also be referred to as abase transceiver station, a node B, or an access point. A base station104 may be a station that communicates with the UEs 102 and may also bereferred to as a base station, a node B, an access point, and the like.

The base stations 104 communicate with the UEs 102 as indicated bycommunication signals 106. A UE 102 may communicate with the basestation 104 via an uplink and a downlink. The downlink (or forward link)refers to the communication link from the base station 104 to the UE102. The uplink (or reverse link) refers to the communication link fromthe UE 102 to the base station 104. The base stations 104 may alsocommunicate with one another, directly or indirectly, over wired and/orwireless connections, as indicated by communication signals 108.

UEs 102 may be dispersed throughout the wireless network 100, as shown,and each UE 102 may be stationary or mobile. The UE 102 may also bereferred to as a terminal, a mobile station, a subscriber unit, etc. TheUE 102 may be a cellular phone, a smartphone, a personal digitalassistant, a wireless modem, a laptop computer, a tablet computer, etc.The wireless communication network 100 is one example of a network towhich various aspects of the disclosure apply.

Each base station 104 may provide communication coverage for aparticular geographic area. In 3GPP, the term “cell” can refer to thisparticular geographic coverage area of a base station and/or a basestation subsystem serving the coverage area, depending on the context inwhich the term is used. In this regard, a base station 104 may providecommunication coverage for a macro cell, a pico cell, a femto cell,and/or other types of cell. A macro cell generally covers a relativelylarge geographic area (e.g., several kilometers in radius) and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A pico cell may generally cover a relatively smallergeographic area and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A femto cell may also generallycover a relatively small geographic area (e.g., a home) and, in additionto unrestricted access, may also provide restricted access by UEs havingan association with the femto cell (e.g., UEs in a closed subscribergroup (CSG), UEs for users in the home, and the like). A base stationfor a macro cell may be referred to as a macro base station. A basestation for a pico cell may be referred to as a pico base station. Abase station for a femto cell may be referred to as a femto base stationor a home base station.

In the example shown in FIG. 1, the base stations 104 a, 104 b and 104 care examples of macro base stations for the coverage areas 110 a, 110 band 110 c, respectively. The base stations 104 d and 104 e are examplesof pico and/or femto base stations for the coverage areas 110 d and 110e, respectively. As will be recognized, a base station 104 may supportone or multiple (e.g., two, three, four, and the like) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a base station, a UE, or thelike) and sends a transmission of the data and/or other information to adownstream station (e.g., another UE, another base station, or thelike). A relay station may also be a UE that relays transmissions forother UEs. A relay station may also be referred to as a relay basestation, a relay UE, a relay, and the like.

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the base stations 104 may havesimilar frame timing, and transmissions from different base stations 104may be approximately aligned in time. For asynchronous operation, thebase stations 104 may have different frame timing, and transmissionsfrom different base stations 104 may not be aligned in time.

In some implementations, the wireless network 100 utilizes orthogonalfrequency division multiplexing (OFDM) on the downlink andsingle-carrier frequency division multiplexing (SC-FDM) on the uplink.OFDM and SC-FDM partition the system bandwidth into multiple (K)orthogonal subcarriers, which are also commonly referred to as tones,bins, or the like. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K) may bedependent on the system bandwidth. For example, K may be equal to 72,180, 300, 600, 900, and 1200 for a corresponding system bandwidth of1.4, 3, 5, 10, 15, or 20 megahertz (MHz), respectively. The systembandwidth may also be partitioned into sub-bands. For example, asub-band may cover 1.08 MHz, and there may be 1, 2, 4, 8 or 16 sub-bandsfor a corresponding system bandwidth of 1.4, 3, 5, 10, 15, or 20 MHz,respectively.

Referring now to FIG. 2, there is shown an example of a system that maybe used to enhance the efficiency of use of available bandwidth inwireless communications channels between one or more UEs 102 and one ormore base stations 104, as discussed above with respect to FIG. 1. FIG.2 illustrates one base station 104 and one UE 102 for purposes ofsimplicity of discussion, though it will be recognized that embodimentsof the present disclosure may scale to many more UEs 102 and/or basestations 104. The UE 102 and the base station 104 may communication witheach other at various frequencies. For example, in one embodiment the UE102 and the base station 104 may communicate at sub-6 GHz frequencies,while in another embodiment at above 6 GHz frequencies, to name just twoexamples.

UE 102 broadcasts a sounding reference signal (SRS) 202 that is receivedby base station 104. In an embodiment, the SRS 202 may be anomni-directional transmission, while in another embodiment the SRS 202may be a wide-beam transmission. Upon receipt of the SRS 202, the basestation 104 is able to gather from the SRS 202, either explicitly orimplicitly, channel information for the uplink channel between the UE102 and the base station 104. The base station 104 may then use thatuplink channel information to train its antennas to beamform a downlink204 to the same UE 102.

To derive the most advantage from reciprocity (applying channelinformation obtained from the SRS 202 in the uplink), the base station104 may rapidly re-apply that information (by training) for beamforming(or focusing) a downlink transmission to the UE 102 so as to minimizethe effects of channel decorrelation. To assist in therapid-reapplication of the channel information in the downlink,embodiments of the present disclosure utilize a short subframestructure. Referring now to FIG. 3, an exemplary subframe structure 300is illustrated that operates within a short timeframe so as to minimizethe effects of decorrelation in the channel. In an embodiment, the shorttimeframe may be approximately 500 microseconds, though it may also beshorter or longer than that. The short timeframe allows the base station104 to essentially “freeze” the channel state for the duration of thesubframe, during which the base station 104 may train and form the beamfor the downlink and then provide a downlink burst.

Communications between UE 102 and base station 104 can be divided in thetime domain into subframes (SFs) 300, such as the SF 300 illustrated inFIG. 3. A single subframe is illustrated in FIG. 3 for ease ofillustration; as will be recognized, the structure of the SF 300 isscalable to any number of subframes as necessary or desired. Each SF 300is divided into an uplink (UL) portion 302 and a downlink (DL) portion304, separated by a transition portion U/D. As part of the UL portion302, the UE 102 may send various types of signals to the base station104. These may include, for example, an SRS (used here for transmitbeamforming at the base station and in place of the uplink DMRS), uplinkdata, and optionally requests for information. The transition portionU/D is provided between the UL portion 302 and the DL portion 304.During the DL portion, the base station 104 sends various types ofsignals to the UE 102, including for example a user-equipment referencesignal (UERS) and downlink data (e.g., in a downlink burst).

In some embodiments, the base station 104 may use the SRS in the ULportion 302 derive multiple pieces of information that facilitate thedownlink between the UE 102 and the base station 104. For example, basedon the SRS the base station 104 having multiple antennas is able totrain its antennas to beamform the DL data transmitted back to the UE102 so that, for instance, interference with other wirelesscommunication devices in the range of the base station 104 is reduced.Beamforming relies on information about the channel between the UE 102and the base station 104 that the base station 104 derives from theuplink SRS and then applies to the downlink based on reciprocity. Thebase station 104 can retrain its antennas as the channel changes overtime (e.g., periodically or randomly), for example according tosubsequent SRS received from the UE 102. This may happen, for example,if the UE 102 is moving or if other moving objects enter or leave thearea/interfere with the uplink (or downlink) channel According toembodiments of the present disclosure, the subframe 300 is provided aspart of a synchronous system, such that the subframe 300 is providedrepeatedly over time so that the base station 104 may retrain the beamsto accommodate for UE 102 motion and channel decorrelation related tothat movement (and/or other influences).

Channel reciprocity may allow the base station 104 to apply informationabout the channel in the UL direction to estimate one or more channelproperties in the DL direction, which can be used to beamform the DLtransmissions. In this manner, the base station 104 can train itsantennas based on the SRS from the UE 102. The SRS may further includeinformation that allows the base station 104 to demodulate data receivedfrom the UE 102 during the UL portion of the SF 300. The base station104 may additionally determine, from the SRS, scheduling informationthat allows the base station 104 to schedule future SFs 300 (e.g.,frequency bands, etc.) for communicating with the UE 102. Exemplarystructures for the SF 300 are described in U.S. patent application Ser.No. 14/866,794, filed on an even date herewith, and the entirety ofwhich is hereby incorporated by reference.

FIG. 4 is a diagram of a portion of the wireless network 100 accordingto embodiments of the present disclosure. The wireless network 100 mayinclude base stations 402 and 406, and user equipments (UEs) 404 and408.

According to aspects of the present disclosure, communication between atarget receiver, such as the UE 404, and a target sender, such as thebase station 402, accounts for interference experienced by the targetreceiver. In the illustrated embodiment of FIG. 4, base station 402 isin communication with UE 404, and the base station 406 is incommunication 408. For example, the base station 406 serves downlinkcommunication, as indicated by the communication signal 410, to the UE408. As a result of the base station 406 communicating with the UE 408,interference can be experienced by other UEs in the network, includingUE 404. Despite the fact that base station 406 may focus the beam 410 inthe direction of UE 408, the UE 404 can receive interference from aninterfering signal 412. The interfering signal 412 can be a component ofthe beam 410, such as a side lobe or back lobe of a beam transmitted bya directional antenna of the base station 406. The UE 404 receives theinterfering signal 412 and determines the spatial direction associatedtherewith. Mathematically, the UE 404 can determine the correlationmatrix R_(nn) of the noise.

The UE 404 may receive interfering signals from more than one basestation that are in communication with respective UEs. For example, theUE 404 can receive interfering signals 412 and 472 from base stations406 and 476, respectively. Base station 406 is in communication with UE408 (as indicated by the beam 410), and base station 476 is incommunication with UE 478 (as indicated by the beam 480). Theinterfering base stations (e.g., base stations 406 and 476) can bevariously spatially positioned relative to the UE 404. The presentdisclosure contemplates that the UE 404 and/or its serving base station402 can account for the spatial directions of multiple interferingsignals received from multiple base stations.

While the present disclosure may refer to cellular network including UEsand base stations, it is understood that the features described hereincan be generally applied to communication between any target receiverand any target sender in a wireless communication network. For example,the features described herein could be implemented in the WiFi systemfor communication between a UE and a base station or access point.

The UE 404 can account for the spatial direction of the interferingsignal 412 when it transmits a sounding reference signal (SRS) to thebase station 402. In some embodiments, the UE 404 can include more thanone antenna, such that directionally specific information can becommunicated. For example, the UE 404 can be operable to transmitinformation indicative of which spatial direction(s) are undesirable orless desirable (e.g., because of interference) and/or which spatialdirection(s) are more desirable (e.g., an direction that experience lessinterference).

FIG. 5 is a flow diagram of a method 500 of wireless communication.Steps of the method 500 can be executed by a computing device (e.g., aprocessor, processing circuit, and/or other suitable component) of awireless communication device, such as the UE 404, for example. Themethod 500 can be better understood with reference to FIGS. 1-4 and7-13. As illustrated, the method 500 includes a number of enumeratedsteps, but embodiments of the method 500 may include additional stepsbefore, after, and in between the enumerated steps. In some embodiments,one or more of the enumerated steps may be omitted or performed in adifferent order.

At step 510, the method 500 includes receiving, at a wirelesscommunication device (e.g., the UE 404) in communication with a firstbase station (e.g., the base station 402), an interfering signal from asecond base station (or other base stations) (e.g., the base station406). At step 520, the method 500 includes determining, at the wirelesscommunication device, a spatial direction of the interfering signal. Atstep 530, the method 500 includes transmitting, with the wirelesscommunication device, a signal to the first base station based on thespatial direction of the interfering signal. Transmitting the signal tothe first base station (step 530) can include transmitting a beamformedsounding reference signal (SRS) to the first base station, as describedin greater detail with respect to FIG. 8.

The beamformed SRS can have a spatial direction that limits interferencefrom the interfering signal. The beamformed SRS can be established basedon a beam codebook. The beamformed SRS can also be established based ona calculation associated with interference from the interfering signal.Transmitting the signal to the first base station (step 530) can includetransmitting, with the wireless communication device, multiple signalsto the first base station based on the spatial direction of theinterfering signal. Transmitting multiple signals is described ingreater detail with respect to FIGS. 12 and 13. The multiple signals canbe transmitted simultaneously or sequentially over time. Transmittingthe multiple signals can include transmitting at least one soundingreference signal (SRS) via a first antenna of the mobile communicationdevice at a first time; and transmitting at least one SRS via a secondantenna of the mobile communication device at a second time. At step540, the method 500 includes receiving, at the first wirelesscommunication device, a downlink communication from the base station.The the downlink communication layers are beamformed in the spatialdirection(s) based on the signal transmitted to the first base station.

FIG. 6 is a flow diagram of a method 600 of wireless communication.Steps of the method 600 can be executed by a computing device (e.g., aprocessor, processing circuit, and/or other suitable component) of awireless communication device, such as the base station 402, forexample. The method 600 can be better understood with reference to FIGS.1-4 and 7-13. As illustrated, the method 600 includes a number ofenumerated steps, but embodiments of the method 600 may includeadditional steps before, after, and in between the enumerated steps. Insome embodiments, one or more of the enumerated steps may be omitted orperformed in a different order.

At step 610, the method 600 includes receiving, at a first base station(e.g., the base station 402) a signal from a wireless communicationdevice (e.g., UE 404). The signal may be based on a spatial direction ofan interfering signal received by the wireless communication device froma second base station (or other base stations). Receiving a signal froma wireless communication device (step 610) can include receiving abeamformed sounding reference signal (SRS), as described in greaterdetail with respect to FIG. 8. The beamformed SRS can have a spatialdirection that limits interference at the wireless communication devicefrom the interfering signal. At step 620, the method 600 includesestablishing, at the first base station, a communication channel betweenthe first base station and wireless communication device based on thebeamformed SRS. At step 630, the method 600 includes transmitting, withthe first base station, a downlink communication to the wirelesscommunication device. The downlink communication layers are beamformedin the spatial direction(s) based on the signal received from thewireless communication device. The downlink communication can betransmitted using at least one antenna of the first base stationoperable to transmit along the spatial direction based on the signalreceived from the wireless communication device, the first base stationhaving a plurality of antennas operable to transmit along differentspatial directions. Transmitting a downlink communication (step 630) caninclude transmitting the downlink communication along a path selectedfrom among a plurality of paths based on the signal received from thewireless communication device. The downlink communication can beestablished based on a beam codebook and/or a reciprocal beamcalculation.

FIG. 7 illustrates a portion of the wireless network 100. The UE 404receives interference from the interfering signal 412 from theinterfering base station 406. The UE 404 can determine the direction(s)associated with the interfering signal 412 and direction(s) that do notsuffer from interference. Based on the determined direction of theinterfering signal 412, the UE 404 can determine desirable andundesirable directions to receive signals from its serving base station(e.g., the base station 402 of FIG. 4). In this manner, the UE 404 candirect its serving base station to use a beam that does not collide withthe interfering signal 412. The UE 404 can also determine the directionof an undesirable receive beam u₂. The undesirable direction, relativeto the UE 404 and interfering signal 412 in FIG. 7, includes the lobes416 a and 416 b. As illustrated, the lobe 416 b captures the power fromthe interfering signal 412. The UE 404 can direct its serving basestation (e.g., the base station 402 of FIG. 4) to avoid transmittingalong the direction of undesirable beam u₂. The UE 404 can alsodetermine the direction of a desirable receive beam u₁. The desirabledirection, relative to the UE 404 and interfering signal 412 in FIG. 7,includes the lobes 414 a and 414 b. The lobes 414 a and 414 b capturerelatively little power from the interfering signal 412. The UE 404 candirect its serving base station to transmit along the direction of thedesirable beam u₁. In the illustrated embodiment, the desirable spatialdirection associated with beam u₁ is oriented relative to theinterfering signal 412 such that the interference is substantially orcompletely nulled. Transmission along the direction of the desirablebeam u₁ thus optimizes the spatial direction to minimize theinterference from the interfering signal 412.

FIG. 8 illustrates a portion of the wireless network 100. The UE 404 cantransmit a sounding beam or beamformed (BF) SRS 418 to its base station402. The BF-SRS 418 can have spatial direction(s) based on theinterference from the interfering signal 412. The UE 404 can determinethe spatial direction of the BF-SRS 418 to be the same as the directionof the lobes 414 a and 414 b, which do not encompass (or minimize) theinterfering signal 412 from the interfering base station 406. When theUE 404 receives interfering signals from multiple base stations, theBF-SRS 418 can have spatial direction(s) that limits interference fromthe multiple interfering signals. Transmitting the BF-SRS can becontrasted with an omni-directional sounding beam 420 illustrated inFIG. 9. In the embodiment of FIG. 9, the UE 484 does not communicate adirection of the interference from interfering signal 412 (or preferreddirection of communication) with the sending of a single sounding beam420. However, as discussed below with respect to FIG. 13, in someimplementations omni-directional sounding beams can be utilized tocommunicate interference information and/or desired spatialcommunication direction(s).

Referring again to FIG. 8, the base station 402 can use the SRS toestablish a communication channel with the UE 404, including channelestimation, that limits interferences from the interfering signal 412.In some embodiments, the BF-SRS 418 is established based on a beamcodebook. In some embodiments, one or more parameters (magnitude,direction, etc.) of the BF-SRS 418 are calculated based on theinterference received at the UE 404. For example, the calculations basedon interference can determine to transmit the BF-SRS 418 along the nullspace of the correlation matrix R_(nn) or more generally, based onwhitened channel estimate, which is along a spatial direction thatlimits interference from the interfering signal 412. The calculationsbased on interference can also transmit the BF-SRS 418 such that the UE404 sounds the whitened channel R_(nn) ^(−½)H, which refers to awhitened channel that has been modified such that the interference onthe channel has a Gaussian distribution.

FIG. 10 illustrates a portion of the wireless network 100. The basestation 402 transmits a downlink communication to the UE 404 based onthe BF-SRS received at the base station 402. The downlink communicationcomprises a narrow beam along the spatial direction of lobes 414 a, 414b, as shown. Downlink communications may comprise one or more layers.The downlink communication layers are beamformed in the spatialdirection(s) based on the BF-SRS transmitted to the base station 402.Accordingly, the UE 404 receives the downlink communication in a mannerthat limits interference from the interfering signal 412. The downlinkcommunication can include one or more layers that are beamformed indirection(s) based on the interfering signal(s). In some embodiments,the downlink communication can include one or more layers that arebeamformed in directions based on the sounding beam transmitted by theUE 404 that does not necessarily account for the interfering signal(s).For example, the downlink communication can include both layer(s) thatdo consider interfering signals and layer(s) that do not. In thatregard, one or more layers of the downlink communication can bebeamformed in directions based on channel estimation and/or other stepsperformed by the UE 404 and/or the the base station 402 to establishcommunication that do not account for the directionality of interferingsignals received by the UE 404. The beam associated with downlinkcommunication can be a reciprocal beam that is determined based on thereceived BF-SRS and a beam codebook. In some embodiments, one or moreparameters (magnitude, direction, etc.) of the downlink communicationbeam are determined using reciprocal beam calculation.

FIG. 11 illustrates a portion of the wireless network 100. The portionof the wireless network 100 shown in FIG. 11 includes obstructions 422.Obstructions 422 can be man-made or natural formations, such asbuildings, mountains, etc., that are physically interposed between thebase station 402 and the UE 404. Because of one or more obstructions422, the base station 402 may encounter significant interference inattempts to transmit to the UE 404 along a direct path. Thus, the basestation 402 may transmit along path 424 or 426 in an effort tocommunicate with the UE 404. The transmission beams along paths 424 and426 can be deflected by one or more of the obstructions 422 beforereaching the UE 404. According to aspects of the present disclosure, thebase station 402 can choose to transmit along the path that limits theinterference from the interfering signal 412 (e.g., path 426 in FIG.11). Thus, the base station 402 can determine the direction that limitsinterference from among a plurality of available paths between the basestation 402 and the UE 404 based on a received SRS from the UE 404.

FIG. 12 illustrates a communication environment 490 associated with aninterference aware multiplexing scheme. In that regard, multiplexing canbe implemented when the communication channel has relatively low levelsof interference that allow the channel to support multipletransmissions. For example, in a single-user (SU) multiple inputmultiple output (MIMO) context, the channel rank associated with the UE404 and its serving base station may be greater than one (1). A channelrank greater than one may be indicative channel with sufficiently lowinterference to support multiple transmissions.

The UE 404 may transmit multiple signals to its serving base station,based on the direction of an interfering signal. As shown in FIG. 12,for example, UE 404 can transmit SRS beams 430 and 431 during the uplinkportion 434 of the subframe 432. While two SRS beams 430 and 431 areillustrated in FIG. 12, it is understood that any suitable number of SRSbeams may be transmitted. In that regard, the SRS beams 430 and 431 maybe multiplexed using non-orthogonal or orthogonal methods described inU.S. patent application Ser. No. 14/866,778, filed on an even dateherewith, and the entirety of which is hereby incorporated by reference.For example, the multiple beams may be sent simultaneously orsequentially over time. In various embodiments, the multiple beams maybe transmitted by one antenna or multiple antennas of the UE 404 (suchas one or both of antennas 428 and 429). While FIG. 12 illustrates thatthe UE 404 has two antennas 428 and 429, the UE 404 can have one or morethan two antennas in other embodiments.

Each SRS may be transmitted by a different transmit antenna or multipleSRSs can be transmitted by multiple antennas according to a methodgoverned by a precode vector. In some embodiments, at least one soundingreference signal (SRS) is transmitted by a first antenna (e.g., theantenna 428) of the UE 404 at a first time and at least one SRS istransmitted by a second antenna (e.g., the antenna 429) of the UE 404 ata second time. In some embodiments, the SRS signals 430, 431 may betransmitted by multiple antennas with different phases. For example, SRS430 may be transmitted by both antennas 428 and 429 with a first phase,and SRS 431 may be transmitted by both antennas 428 and 429 with asecond phase. The phases of the SRS beams 430 and 431 can be indicativeof the direction of the beams. The phases are mathematically shown bythe example vectors [1, e^(jθ)] and [1,1] operating on SRS 430 and SRS431, respectively. Thus, one, more than one, or all of SRSs transmittedby the UE 404 are beamformed in a direction based on an interferingsignal. Accordingly, the serving base station that receives the multipleSRS beams transmits downlink communication 438 to the UE 404 during thedownlink portion 436 of the subframe 432 in a manner that limitsinterference received at the UE 404 (e.g., from an interfering signal,as described herein).

FIG. 13 illustrates a communication environment 492 associated with aninterference aware multiplexing scheme. The UE 404 includes multipleantennas but is operable to transmit on one antenna at a time. Forexample, the UE 404 can transmit on antenna 440 at a first time and onantenna 442 at a second time. Such a system can be implemented byswitching the transmit chain, comprising the electronic components, suchas the power amplifier and other components, across the transmitantennas. Because only one antenna is active at a time, eachtransmission may be omni-directional. As illustrated in FIG. 13, at afirst segment 458 of the uplink portion 454 of the subframe 452, theantenna 440 transmits the two SRS beams 444 and 446. At a second segment460 of the uplink portion 454, the antenna 442 transmits the two SRSbeams 448 and 450. The SRS beams 444 and 446, and the SRS beams 448 and450 can correspond to different MIMO streams and can be multiplexed inan orthogonal or non-orthogonal manner, as described with respect toFIG. 12. The receiving base station that receives SRS beams from the twosegments 458 and 460 from the antennas 440 and 442 (as shown in FIG. 13)in effect receives the SRS beams 430 and 431 described in FIG. 12. Inthat regard, transmission of the SRS beams 444, 446, 448, and 450 mayhave different phases. For example, during the first segment 458, theantenna 440 may transmit SRS 444 and SRS 446 with a first phase. Duringthe second segment 460, the antenna 442 may transmit SRS 448 and SRS 450with a second phase. While the SRS beams 444, 446, 448, and 450 are eachlabeled distinctly, it is understood that SRS beams 444 and 448 may beidentical except for differences in phase. Similarly, it is understoodthat the SRS beams 446 and 450 may be identical except for differencesin phase. The phases of the SRS beams 444, 446, 448, and 450 can beindicative of the direction of the beams. The phases are mathematicallyshown by the example vectors operating on SRS beams 444, 446, 448, and450 during the segments 458 and 460. Accordingly, the serving basestation that receives the multiple SRS beams transmits a beamformeddownlink communication 460 to the UE 404 during the downlink portion 456of the subframe 452 in a manner based on the received SRS beams. Thesame technique could be applied to provide frequency divisionmultiplexing (FDM) of interference aware SRS.

FIG. 14 is a block diagram of an exemplary wireless communication device1400 according to embodiments of the present disclosure. The wirelesscommunication device 1400 may be a base UE 102 or 404 as discussedabove. As shown, the UE 102 may include a processor 1402, a memory 1404,an interference detection module 1408, a transceiver 1410 (including amodem 1412 and RF unit 1414), and an antenna 1416. These elements may bein direct or indirect communication with each other, for example via oneor more buses.

The processor 1402 may include a central processing unit (CPU), adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a controller, a field programmable gate array (FPGA)device, another hardware device, a firmware device, or any combinationthereof configured to perform the operations described herein withreference to UEs 102 introduced above with respect to FIG. 1 anddiscussed in more detail above. In particular, the processor 1402 may beutilized in combination with the other components of the UE 102,including interference detection module 1408, to perform the variousfunctions associated with determining whether there is interference inthe uplink channel, what spatial direction interference is coming from,and how to structure an SRS to the base station 104/402 to avoid theinterference as described in greater detail above. The processor 1402may also be implemented as a combination of computing devices, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The memory 1404 may include a cache memory (e.g., a cache memory of theprocessor 1402), random access memory (RAM), magnetoresistive RAM(MRAM), read-only memory (ROM), programmable read-only memory (PROM),erasable programmable read only memory (EPROM), electrically erasableprogrammable read only memory (EEPROM), flash memory, solid state memorydevice, hard disk drives, other forms of volatile and non-volatilememory, or a combination of different types of memory. In an embodiment,the memory 1404 includes a non-transitory computer-readable medium. Thememory 1404 may store instructions 1406. The instructions 1406 mayinclude instructions that, when executed by the processor 1402, causethe processor 1402 to perform the operations described herein withreference to the UEs 102 in connection with embodiments of the presentdisclosure. Instructions 1406 may also be referred to as code. The terms“instructions” and “code” should be interpreted broadly to include anytype of computer-readable statement(s). For example, the terms“instructions” and “code” may refer to one or more programs, routines,sub-routines, functions, procedures, etc. “Instructions” and “code” mayinclude a single computer-readable statement or many computer-readablestatements.

The interference detection module 1408 may be used for various aspectsof the present disclosure. For example, the interference detectionmodule 1408 may determine that there is interference in the uplinkchannel due to, for example, other base stations 406, 476 transmittingto other UEs 408, 478 and creating sidelobe or backlobe transmissions inthe process. The interference detection module 1408 may then use thedetermined interference to structure a beamformed SRS to the basestation 104/402 based on the spatial direction of the interference.

As shown, the transceiver 1410 may include the modem subsystem 1412 andthe radio frequency (RF) unit 1414. The transceiver 1410 can beconfigured to communicate bi-directionally with other devices, such asbase stations 104. The modem subsystem 1412 may be configured tomodulate and/or encode the data from the interference detection module1408 and other aspects of the UE 102, such as processor 1402 and/ormemory 1404, according to a modulation and coding scheme (MCS), e.g., alow-density parity check (LDPC) coding scheme, a turbo coding scheme, aconvolutional coding scheme, etc. The RF unit 1414 may be configured toprocess (e.g., perform analog to digital conversion or digital to analogconversion, etc.) modulated/encoded data from the modem subsystem 1412(on outbound transmissions) or of transmissions originating from anothersource such as a UE 102 or a base station 104. Although shown asintegrated together in transceiver 1410, the modem subsystem 1412 andthe RF unit 1414 may be separate devices that are coupled together atthe UE 102 to enable the UE 102 to communicate with other devices.

The RF unit 1414 may provide the modulated and/or processed data, e.g.data packets (or, more generally, data messages that may contain one ormore data packets and other information), to the antenna 1416 fortransmission to one or more other devices. This may include, forexample, transmission of an SRS according to embodiments of the presentdisclosure. The antenna 1416 may further receive data messagestransmitted from other devices and provide the received data messagesfor processing and/or demodulation at the transceiver 1410. AlthoughFIG. 14 illustrates antenna 1416 as a single antenna, antenna 1416 mayinclude multiple antennas of similar or different designs in order tosustain multiple transmission links.

FIG. 15 illustrates a block diagram of an exemplary base station 104according to the present disclosure. The base station 104 may include aprocessor 1502, a memory 1504, a beamforming module 1508, a transceiver1510 (including a modem 1512 and RF unit 1514), and an antenna 1516.These elements may be in direct or indirect communication with eachother, for example via one or more buses.

The processor 1502 may have various features as a specific-typeprocessor. For example, these may include a CPU, a DSP, an ASIC, acontroller, a FPGA device, another hardware device, a firmware device,or any combination thereof configured to perform the operationsdescribed herein with reference to the base stations 104 introduced inFIG. 1 above. The processor 1502 may also be implemented as acombination of computing devices, e.g., a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The memory 1504 may include a cache memory (e.g., a cache memory of theprocessor 1502), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, asolid state memory device, one or more hard disk drives, memristor-basedarrays, other forms of volatile and non-volatile memory, or acombination of different types of memory. In some embodiments, thememory 1504 may include a non-transitory computer-readable medium. Thememory 1504 may store instructions 1506. The instructions 1506 mayinclude instructions that, when executed by the processor 1502, causethe processor 1502 to perform operations described herein with referenceto a base station 104 in connection with embodiments of the presentdisclosure. Instructions 1506 may also be referred to as code, which maybe interpreted broadly to include any type of computer-readablestatement(s) as discussed above with respect to FIG. 2.

The beamforming module 1508 may be used for various aspects of thepresent disclosure. For example, the beamforming module 1508 may extractinformation from an SRS received from a UE 102 and train beamforming ateach antenna 1516 based on the extracted information.

As shown, the transceiver 1510 may include the modem subsystem 1512 andthe radio frequency (RF) unit 1514. The transceiver 1510 can beconfigured to communicate bi-directionally with other devices, such asUE 102 and/or another core network element. The modem subsystem 1512 maybe configured to modulate and/or encode data according to a MCS, e.g., aLDPC coding scheme, a turbo coding scheme, a convolutional codingscheme, etc. The RF unit 1514 may be configured to process (e.g.,perform analog to digital conversion or digital to analog conversion,etc.) modulated/encoded data from the modem subsystem 1512 (on outboundtransmissions) or of transmissions originating from another source suchas a UE 102. Although shown as integrated together in transceiver 1510,the modem subsystem 1512 and the RF unit 1514 may be separate devicesthat are coupled together at the base station 104 to enable the basestation 104 to communicate with other devices.

The RF unit 1514 may provide the modulated and/or processed data, e.g.data packets (or, more generally, data messages that may contain one ormore data packets and other information), to the antenna 1516 fortransmission to one or more other devices. This may include, forexample, transmission of information to complete attachment to a networkand communication with a camped UE 102 according to embodiments of thepresent disclosure. The antenna 1516 may further receive data messagestransmitted from other devices and provide the received data messagesfor processing and/or demodulation at the transceiver 1510. AlthoughFIG. 15 illustrates antenna 1516 as a single antenna, antenna 1516 mayinclude multiple antennas of similar or different designs in order tosustain multiple transmission links.

Further embodiments of the present disclosure include a method forreceiving a signal from a wireless communication device at a first basestation, the received signal based on a spatial direction of aninterfering signal received by the wireless communication device from asecond base station, and transmitting from the first base station adownlink communication to the wireless communication device, whereindownlink communication layers are beamformed in a spatial directionbased on the signal received from the wireless communication device.

In some embodiments the received signal may be a beamformed SRS. Thebeamformed SRS may have a spatial direction that limits interference atthe wireless communication device from the interfering signal. The firstbase station may further establish a communication channel betweenitself and the wireless communication device based on the beamformedSRS. The base station may have a plurality of antennas operable totransmit along different spatial directions, and the downlinkcommunication from the base station to the wireless communication devicemay be transmitted using at least one antenna of the first base stationoperable to transmit along the spatial direction determined based on thesignal received from the wireless communication device. Transmitting thedownlink communication from the base station to the wirelesscommunication device may include transmitting the downlink communicationalong a path selected from among a plurality of paths based on thesignal received from the wireless communication device. The downlinkcommunication may be established based on a beam codebook or based on areciprocal beam calculation.

Further embodiments of the present disclosure include a base stationcomprising a transceiver operable to receive, from a wirelesscommunication device, a signal based on a spatial direction of aninterfering signal received by the wireless communication device from asecond base station, and to transmit to the wireless communicationdevice a downlink communication which has layers that are beamformed ina spatial direction based on the signal received from the wirelesscommunication device. The signal received from the wirelesscommunication device may be a beamformed SRS, which may have a spatialdirection that limits interference at the wireless communication devicefrom the interfering signal. The base station may further comprise acomputing device in communication with the transceiver which is operableto establish a communication channel with the wireless communicationdevice based on the beamformed SRS.

The base station may further comprise a plurality of antennas incommunication with the transceiver that are operable to transmit alongdifferent spatial directions. The downlink communication may betransmitted using at least one antenna operable to transmit along thespatial direction based on the signal received from the wirelesscommunication device. The base station may transmit the downlinkcommunication along a path selected from among a plurality of pathsbased on the signal received from the wireless communications device.The base station may further comprise a computing device operable toestablish the downlink communication based on a beam codebook, or basedon a reciprocal beam calculation.

Further embodiments of the present disclosure include a base stationcomprising means for receiving from a wireless device a signal based ona spatial direction of an interfering signal received by the wirelesscommunication device from a second base station and means fortransmitting to the wireless communication device a downlinkcommunication whose layers are beamformed in a spatial direction basedon the signal received from the wireless communication device. Thesignal received from the wireless communication device may be abeamformed SRS, which may have a spatial direction that limitsinterference at the wireless communication device from the interferingsignal. The base station may further comprise means for establishing acommunication channel with the wireless communication device based onthe beamformed SRS.

The base station may further comprise means for transmitting alongdifferent spatial directions, and the downlink communication may betransmitted along a spatial direction based on the signal received fromthe wireless communication device. The base station may further comprisemeans for transmitting the downlink communication along a path selectedfrom among a plurality of paths based on the signal received from thewireless communication device. The base station may further comprisemeans for establishing the downlink communication based on a beamcodebook or based on a reciprocal beam calculation.

Further embodiments of the present disclosure include a wirelesscommunication device in communication with a first base station,comprising means for receiving an interfering signal from a second basestation, means for determining a spatial direction of the interferingsignal, and means for transmitting a signal to the first base stationbased on the spatial direction of the interfering signal. This signalmay be a beamformed SRS, which may have a spatial direction that limitsinterference from the interfering signal. The wireless communicationdevice may further include means for establishing the beamformed SRSbased on a beam codebook or based on a calculation associated withinterference from the interfering signal.

The wireless communication device may further comprise means forreceiving a downlink communication from the first base station, thedownlink communication layers being beamformed in a spatial directionbased on the signal transmitted to the first base station. The wirelesscommunication device may further comprise means for transmittingmultiple signals to the first base station based on the spatialdirection of the interfering signal. The means for transmitting multiplesignals may include means for transmitting the multiple signalssimultaneously or sequentially over time. The multiple signals may eachhave a different phase. The wireless communication device may furtherinclude means for transmitting at least one SRS at a first time andmeans for transmitting at least one SRS at a second time.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of [at least one of A, B, or C]means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

As those of some skill in this art will by now appreciate and dependingon the particular application at hand, many modifications, substitutionsand variations can be made in and to the materials, apparatus,configurations and methods of use of the devices of the presentdisclosure without departing from the spirit and scope thereof. In lightof this, the scope of the present disclosure should not be limited tothat of the particular embodiments illustrated and described herein, asthey are merely by way of some examples thereof, but rather, should befully commensurate with that of the claims appended hereafter and theirfunctional equivalents.

What is claimed is:
 1. A method for wireless communication, the methodcomprising: receiving, by a first base station from a wirelesscommunication device, a first signal during a first time period, thefirst signal based on a spatial direction of an interfering signalreceived by the wireless communication device from a second basestation, and the first time period configured for a transmission from afirst antenna of the wireless communication device; receiving, by thefirst base station from the wireless communication device, a secondsignal during a second time period after the first time period, thesecond signal based on the spatial direction of the interfering signal,and the second time period configured for a transmission from a secondantenna of the wireless communication device; and transmitting, by thefirst base station to the wireless communication device, a downlinkcommunication beamformed in a downlink spatial direction based on thefirst signal and the second signal received from the wirelesscommunication device.
 2. The method of claim 1, wherein the receivingthe first signal includes: receiving a beamformed sounding referencesignal (SRS).
 3. The method of claim 2, wherein the beamformed SRS has aspatial direction that limits interference at the wireless communicationdevice from the interfering signal.
 4. The method of claim 2, furthercomprising: establishing, by the first base station, a communicationchannel between the first base station and wireless communication devicebased on the beamformed SRS.
 5. The method of claim 1, wherein the firsttime period and the second time period are sequential time periods. 6.The method of claim 1, wherein the first signal and the second signaleach have a different phase.
 7. The method of claim 1, wherein thetransmitting the downlink communication includes: transmitting thedownlink communication using at least one antenna of a plurality ofantennas of the first base station, the plurality of antennas operableto transmit along different spatial directions including the beamformeddownlink spatial direction.
 8. The method of claim 1, furthercomprising: establishing, by the first base station, the downlinkcommunication based on at least one of a beam codebook or a reciprocalbeam calculation.
 9. A base station comprising: a transceiver configuredto: receive a first signal from a wireless communication device during afirst time period, the first signal based on a spatial direction of aninterfering signal received by the wireless communication device from asecond base station, and the first time period configured for atransmission from a first antenna of the wireless communication device;receive a second signal from the wireless communication device during asecond time period after the first time period, the second signal basedon the spatial direction of the interfering signal, and the second timeperiod configured for a transmission from a second antenna of thewireless communication device; and transmit a downlink communication tothe wireless communication device, the downlink communication beamformedin a downlink spatial direction based on the first signal and the secondsignal received from the wireless communication device.
 10. The basestation of claim 9, wherein the transceiver is further configured toreceive the first signal from the wireless communication device by:receiving a beamformed sounding reference signal (SRS).
 11. The basestation of claim 10, wherein the beamformed SRS has a spatial directionthat limits interference at the wireless communication device from theinterfering signal.
 12. The base station of claim 10, furthercomprising: a processor configured to establish a communication channelwith the wireless communication device based on the beamformed SRS. 13.The base station of claim 9, wherein the first time period and thesecond time period are sequential time periods.
 14. The base station ofclaim 9, wherein the first signal and the second signal each have adifferent phase.
 15. The base station of claim 9, further comprising: aplurality of antennas configured to transmit along different spatialdirections including the beamformed downlink spatial direction, whereinthe downlink communication is transmitted using at least one antenna ofthe plurality of antennas.
 16. The base station of claim 9, furthercomprising: a processor configured to establish the downlinkcommunication based on at least one of a beam codebook or a reciprocalbeam calculation.
 17. A computer-readable medium having program coderecorded thereon, the program code comprising: code for causing a firstbase station to receive, from a wireless communication device, a firstsignal during a first time period, the first signal based on a spatialdirection of an interfering signal received by the wirelesscommunication device from a second base station, and the first timeperiod configured for a transmission from a first antenna of thewireless communication device; code for causing the first base stationto receive, from the wireless communication device, a second signalduring a second time period after the first time period, the secondsignal based on the spatial direction of the interfering signal, and thesecond time period configured for a transmission from a second antennaof the wireless communication device; and code for causing the firstbase station to transmit, to the wireless communication device, adownlink communication beamformed in a downlink spatial direction basedon the first signal and the second signal received from the wirelesscommunication device.
 18. The computer-readable medium of claim 17,wherein the code for causing the first base station to receive the firstsignal is further configured to: receive a beamformed sounding referencesignal (SRS).
 19. The computer-readable medium of claim 18, wherein thebeamformed SRS has a spatial direction that limits interference at thewireless communication device from the interfering signal.
 20. Thecomputer-readable medium of claim 18, further comprising: code forcausing the first base station to establish a communication channelbetween the first base station and wireless communication device basedon the beamformed SRS.
 21. The computer-readable medium of claim 17,wherein the first time period and the second time period are sequentialtime periods.
 22. The computer-readable medium of claim 17, wherein thefirst signal and the second signal each have a different phase.
 23. Thecomputer-readable medium of claim 17, wherein the code for causing thefirst base station to transmit the downlink communication is furtherconfigured to: transmit the downlink communication using at least oneantenna of a plurality of antennas of the first base station, theplurality of antennas operable to transmit along different spatialdirections including the beamformed downlink spatial direction.
 24. Thecomputer-readable medium of claim 17, further comprising: code forcausing the first base station to establish the downlink communicationbased on at least one of a beam codebook or a reciprocal beamcalculation.
 25. A base station comprising: means for receiving, from awireless communication device, a first signal during a first timeperiod, the first signal based on a spatial direction of an interferingsignal received by the wireless communication device from a second basestation, and the first time period configured for a transmission from afirst antenna of the wireless communication device; means for receiving,from the wireless communication device, a second signal during a secondtime period after the first time period, the second signal based on thespatial direction of the interfering signal, and the second time periodconfigured for a transmission from a second antenna of the wirelesscommunication device; and means for transmitting, to the wirelesscommunication device, a downlink communication beamformed in a downlinkspatial direction based on the first signal and the second signalreceived from the wireless communication device.
 26. The base station ofclaim 25, wherein the means for receiving the first signal is furtherconfigured to: receive a beamformed sounding reference signal (SRS). 27.The base station of claim 26, wherein the beamformed SRS has a spatialdirection that limits interference at the wireless communication devicefrom the interfering signal.
 28. The base station of claim 26, furthercomprising: means for establishing a communication channel between thebase station and wireless communication device based on the beamformedSRS.
 29. The base station of claim 25, wherein the means fortransmitting the downlink communication is further configured to:transmit the downlink communication using at least one antenna of aplurality of antennas of the base station, the plurality of antennasoperable to transmit along different spatial directions including thebeamformed downlink spatial direction.
 30. The base station of claim 25,further comprising: means for establishing the downlink communicationbased on at least one of a beam codebook or a reciprocal beamcalculation.